Wikipedia Article About Yam on Wikipedia
All purpose term for yellow-orange tubers. Similar in size and color to the potato, but nuttier in flavor, it is not to be confused with the Southern sweet yam or sweet potato. Caribbean yams are served boiled, mashed or baked usually mixed with some kind of meat.
Yam is the common name for members of the genus Dioscorea (family Dioscoreaceae). There are more than 150 different varieties of yam. Some species are cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America and Oceania.
The word yam comes from Portuguese inhame or Spanish ñame, which both ultimately derive from the Wolof word nyami, meaning "to eat". They are used in a similar fashion to potatoes, and are sometimes called a potato substitute, though in areas where yams are grown, potatoes are the newer vegetable.
Yam tubers can grow up to seven feet (approx. two meters) in length and weigh up to 150 pounds (68 kg). The yam has a rough skin which is difficult to peel, but which softens after heating. Yam skins vary in color from dark brown to light pink. The majority of the yam is composed of a much softer substance known as the "meat". This substance ranges in color from white to bright orange in ripe yams.
Yams are a primary agricultural commodity in West Africa and New Guinea. They were first cultivated in Africa and Asia about 8000 B.C., probably because they were able to flourish in environments where growing leafy vegetables and keeping livestock was difficult. To this day, the yam tuber remains crucial to survival in the region; it can be stored for four to six months without refrigeration, which makes it a valuable resource for the yearly period of food scarcity at the beginning of the wet season.
Yams are used as food plants by the larvae of some Lepidoptera species including Palpifer sordida.
Dioscorea cayenensis are commonly called "yellow yams", while Dioscorea rotunda which are commonly called "white yams". Both are native to Africa.